Character Hands Stuck During Animation
You need to check 2 things: The keyframes of your IK controller bone, and the Influence value of the IK bone.


First enable the Only Include Channels Relating to Selected Objects button (arrow icon). It will allow you, in the Dopesheet, to only display the keyframes of the selected bones.
Now select the controller bone and switch from an action to another, you'll see that sometimes the controller doesn't have any keyframe at the beginning of the action, which means that, until the next keyframe, the controller will keep the position that it got at the end of the previous action, is it what you want?
Also, you'll see that for some animations you have keyframed the Influence value of the Ik bone, so for some animations it will be at 0 and the IK won't work anymore, and will remain off if you switch to another action that has no keyframe for this value, again if there is no new value keyframed at the beginning only the previous one from the previous animation will be taken into account. Again, is it what you want?


So to fix both these 2 problems you may need to create some keyframes at the beginning of the action: Keyframes for your controller and/or IK Influence value.